This may seem like a odd question. Reguarding the mechanical fuel pump, would it cause any problem if it was running and you shut the supply to the pump off and ran the engine from a electic pump and a different supply line? Would it create vacuum or just pump up to 4 psi and cycle/bypass internally until the fuel supply was restored?

Okay, I will explain myself.. I am considering experimenting with oil in my rear tank. With the cost of fuel I think I can afford the cost of replacing the motor. I have a 2 micron racor filter, and instead of mixing the oil in the stock filter I am adding this filter and a electic inline pump and 3 port switch after the 6 port fuel switch. When I switch to the front tank it puts power to the switches and runs off the front tank and feeds directly into the stock filter. Then switch to the rear tank, it cuts the power to the switches, and runs through the stock supply line through the mechanical pump on the block and to the 2 micron filter. That way I am only mixing a few inches of the supply line worth of fuel in the stock filter. (yes I relocated the return line that goes to the filter to just after so it wont be filling it with oil) It makes me wonder if while I am running off the front tank and the stock pump is not getting any fuel supply, will it cause any problems or just sit and bypass.

 

you have a fuel return line that has to return to the fuel tank hence the 6 line valve
cutting of the fuel before it gets to the mechanical pump will damage the pump
i also believe your asking for trouble splicing into the lines between the stock filter and injector pump , mainly due to air leaks

 

I am not diverting the return line to the tank, the front tank returns to the front tank and the rear tank returns to the rear tank. The 3 way valve takes the supply line and directs it to either filter. I could bypass the mechanical pump altogether, but I thought running the oil through it would be good to add some warmth. But while I am running on the front tank the valve will shut off the supply to it... just not sure if it will matter.

 

I suspect this is not something that many have tried. I suspicsion is that the switching valve wasn't designed to withstand vacuum and so if the pump is left working it would draw some fuel through the valve.

 

i would allow it to pass through the mechanical pump